Ian Blackford has written to the seven Scottish Labour MPs urging them to rule out supporting the offer their leader made to the Prime Minister earlier this week as it would enable a “Tory Brexit” and be “devastating” for the country.

But Labour’s Lesley Laird hit back to accuse the SNP Westminster boss of lying and “political opportunism”.

On Wednesday, Corbyn, in a dramatic and unexpected change to Labour’s position on Brexit, offered to help May get her deal over the line if she made five legally binding commitments – one of which would include joining a customs union.

But Blackford has warned the Labour MPs that accepting May’s deal could lead to GDP being around £9 billion lower and “everything from living standards, jobs, security arrangements [and] market access for our vital services sector” suffering.

Blackford said: “We are less than 50 days away from Brexit date and in Westminster both the Prime Minister and leader of the so-called opposition are leading Scotland and the UK hand in hand off the Brexit cliff-edge.”

“That is a price that Scotland should not be forced to pay. When the Prime Minister returns to Parliament with her deal, Scottish Labour MPs must stand up for Scotland’s economic and social interests, and reject the Prime Minister’s deal and Jeremy Corbyn’s plan to throw his support behind it.

He added: “It is alarming that, despite the overwhelming damage that the Prime Minister’s deal will cause to Scotland, the Labour leader would seek to support the deal. Scotland did not vote for Brexit and our nation must not be dragged out of the EU against our will.

“I call on Scottish Labour MPs to reject the Prime Minister’s deal, support the SNP’s calls for an extension to Article 50 and back a second referendum on EU membership.”

In her response Laird told Blackford that Labour “remain convinced that the best outcome is a General Election to get rid of this appalling Tory government”. She accused the SNP of being “content to see the Tories remain in government”.

Laird also said Corbyn’s proposals were close to those outlined in the Scottish Government’s document Scotland’s Place in Europe.

Laird went on to tell Blackford that it’s wrong to suggest Labour “are somehow enabling a Tory Brexit”. This, she added was “not just disingenuous it is an outright fabrication and political opportunism of the worst kind.”

In her reply to Corbyn, May suggested further talks on the issue of a permanent customs union.

She also offered guarantees on environmental and employment laws.

But some in her own party are unhappy at the prospect of the Prime Minister making a deal for a “soft Brexit” with Labour.

Treasury Chief Secretary Liz Truss suggested she could quit government if No 10 did accept the demand for a customs union.

She told Sky News’ Sophy Ridge On Sunday: “I appreciate Jeremy Corbyn has come to the table but the reality is what he is proposing does not deliver on what we want as a country.”

Asked if she could stay in office if the UK Government backed a customs union she said: “I absolutely do not think that should be our policy.”

Meanwhile, the Government is set to hold another vote on Brexit and May’s deal at the end of the month. This Thursday – Valentine’s Day – was the initial date proposed for the key vote.

The Prime Minister has already committed to coming to Parliament on Wednesday to update MPs on progress made in her bid to amend the withdrawal agreement.

With seemingly little change, May will instead ask MPs to recognise that Brexit talks are still “ongoing”.

Communities Secretary James Brokenshire

Yesterday, the Communities Secretary James Brokenshire confirmed that the Prime Minister would seek to put her revised, finalised deal to the Commons before February 27.

If she failed to do this then MPs would be get a chance to bring forward their own amendments to block a no-deal Brexit or call for a second referendum.

Speaking on BBC One’s Andrew Marr Show, Brokenshire said: “If the meaningful vote has not happened, so in other words things have not concluded, then Parliament would have that further opportunity by no later than February 27.

“I think that gives that sense of timetable, clarity and purpose on what we are doing with the EU – taking that work forward and our determination to get a deal – but equally knowing that role that Parliament very firmly has.”

The Government’s announcement came after shadow Brexit secretary, Keir Starmer told the Sunday Times that Labour would table an amendment on Thursday to force a meaningful vote on a deal before the end of this month.

Starmer said his plan was necessary in order to put a “hard stop” to May “running down the clock” and forcing MPs into choosing between her deal or a hard Brexit two or three days before Britain is due to leave the EU.

“We can’t allow that to happen,” he said. “There needs to be a day when Parliament says that’s it, enough is enough.”

In a separate move, Remain-backing MPs are tabling an amendment which would approve the Prime Minister’s deal as long as she holds a referendum.

The public would get to choose between leaving the EU on May’s terms, or staying permanently.

Labour MP Peter Kyle told The Observer: “The beauty of this plan is that it holds attractions for both Leavers and Remainers. For Leavers, if the deal is confirmed by the British people, it offers a definitive end to the withdrawal process with Brexit sealed once and for all.

“For Remainers, on the other hand, it offers the chance to make the case to stay in the EU to the public, based on facts not promises as before.”

Tory MP Anna Soubry tweeted her support: “We told the Govt weeks ago we would vote for PM’s WithdrawalAgreement on the basis it went back to the people @peoplesvote_uk w #Remain on the ballot paper”.

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